1. Field of the Invention
The present invention relates to a network system including a plurality of vehicle-mounted, microcomputer-based electronic devices interconnected by a transmission channel, and an operating system used in the network system.
2. Description of the Prior Art
A Network systems having a plurality vehicle-mounted, microcomputer-based electronic devices interconnected by a serial transmission bus are known in which data communication is performed in accordance with programs (application programs) written in advance in the electronic devices.
A vehicle-mounted electronic device at the transmit side sends or transmits data to a destination vehicle-mounted electronic device with an identifier affixed to the data. The destination vehicle-mounted electronic device at the receive side performs various processing operations on the basis of the data received. Control is also performed in the same manner as described above. More specifically, a vehicle-mounted electronic device at the transmit side transfers data to be transmitted as control data, and a vehicle-mounted electronic device at the receive side changes the control routine on the basis of the control data.
The foregoing operations at the respective sides are mutually determined in advance, and so when the program at one side (transmit side or receive side) is changed or revised, the program at the other side should be revised. Especially, when a new vehicle-mounted electronic device is incorporated in the network system, data communication is disenabled until the necessary revision is made to the program of any one of the existing vehicle-mounted electronic devices.
Revision or version-up of the programs is tedious and time-consuming from the viewpoint of configuration of a network system for vehicle-mounted electronic devices.
High-speed road-running vehicles generally require various improvements to provide improved reliability and comfortableness. To cope with this requirement, a now vehicle-mounted electronic device equipped with a microcomputer is installed, an optional part or parts are added, or the program of each individual vehicle-mounted electronic device is revised to deal with improvements in any of the existing vehicle-mounted equipments which may be proposed as the technology advances.
Differing from a general computer network system consisting of identical personal computers, the network system for vehicle-mounted electronic devices requires laborious version-up of a program incorporated in each of the existing vehicle-mounted electronic devices to cope with entry of a new vehicle-mounted electronic device.
Due to difficulties, there has been a strong demand for a network system for vehicle-mounted electronic devices which is capable of accepting entry of a now vehicle-mounted electronic device without requiring any revision to the existing programs, and which enables the electronic devices to use information resources and hardware resources in common to deal with the underlying process complexity.